Radio apparatus



March 1, 1938. J McWEENY RADIO APPARATUS Filed NOV. 26, 1937 Patented Mar. 1, 1938 UNETED STATES PATENT OFFIE Claims.

My invention relates to radio receivers and particularly to means intended for use to bring about accurate indication of the tuning of such receivers.

5 Many elements enter into the manufacture of a radio chassis that tend to prevent any certainty in the matter of capacity, and this uncertainty is increased where, as at present, many receiving sets are constructed to pick up frequencies over a wide range; in other words, so-

called all wave receivers.

This variation, notwithstanding the accuracy of machine-made products, occurs principally in the condensers and although they are carefully 1 designed for a uniform minimum and maximum capacity, it seems mechanically impossible to produce exact duplicates, either throughout the range or at individual points.

Furthermore, there is a known variation of ca- 20 pacity from newto used conditions. Temperature, bearing wear, the relieving of internal stresses, etc., cause changes over a period of time.

The same remarks apply to the inductance elements; temperature and moisture serve to cause 25 variations in the electric eifect which are reflected in the tuning of the instrument.

In the commercial production of radio receiving sets, it is, from a practical standpoint, impossible to individually calibrate each set in order 30 that the indicating means shall correspond exactly with the tuning means, practically all sets being delivered from the assembly line with an adjustment that is approximately correct but which may in adjacent sets vary in the indication 35 of the same station as much as 5 kc. and, as

above stated, after the passage of time, this Variation may be greater or less.

The correction of the indicating means as ap- 0 plied to one broadcast band may be accomplished with relative simplicity, but such corrections when applied to another broadcast band would, unfortunately, result in wide variations from accurate indication. I have, therefore, provided each broadcast band with an individual element in the connection between the tuning device and the indicator, each of said elements being capable of adjustment for accurate calibration. Thus, if desired in a more expensive set, each broadcast band may be separately and accurately calibrated relative to a single indicating device. Furthermore, after the passage of time and the consequent readjustment of electrical values, the calibrations may be corrected where required.

5 The invention will be more readily understood by reference to the accompanying drawing, in which;

Fig. 1 is the side elevation of apparatus constructed in accordance with my invention;

Fig. 2 is a plan view thereof;

Fig. 3 is a sectional view on the line 3-3 of Fig. 2; and

Fig. 4 is a sectional View on the line 4-4 of Fig. 3.

In the drawing I have illustrated the essential portions of a radio chassis including -a base ID, a variable condenser ll, adjusted by a tuning knob l2 and having a shaft l3. Connected by gears id to the shaft l3 are a pair of cams l5l6 mounted on a common shaft H. The cams are constructed to provide lateral flanges serving as the active faces of the cams, the flanges being composed of a soft and readily bendable material. Thus the cam contours may be slightly changed by the use of a pair of pliers or some other suitable tool in order to compensate for variations in the tuning indication. While I have shown but two cams, one for each of two broadcast bands, it will be understood that additional cams may be provided for each band in the design of the apparatus.

The indicating means may be any one of a number of types, the one shown being merely a pointer or finger I8 mounted for oscillation over a dial I9. The pointer is carried by a shaft that is splined as at 2| to permit the rearward portion 22 to be reciprocated. A pair of pinions 23-24 are mounted on the shaft and are selectively engaged with the shaft through the spring lugs shown in Figs. 3 and 4. In other words, the shaft 22 carries a pair of spaced plates 25-26 held apart by springs 21 and fixed in position by the cross pin 28. The pinions 2324 are notched as shown in Fig. 3 and the spring lugs are caused to engage one or the other of the pinions by axial movement of the shaft 22. This is brought about through the bell crank 29 pivoted at 30 on a bracket 3| and oscillated through a link 32, rocker 33 and link 34, joined to the shaft 35 that operates the band switch 36. Thus, through the medium of the knob 31 connected to the shaft 35, the band switch may be shifted and, at the same time, the pinion 23 or 24 is connected to the shaft of the tuning indicator. Racks 3839 are mounted for sliding movement in a guide piece 40, the racks having rollers on their ends that engage the active surfaces of the flanges on the cams |5-|6.

In the more inexpensive receiving sets, it may be satisfactory to provide merely for correction of the tuning of the main broadcast band in which case only one cam with its bendable flange will be provided. If, however, a plurality of bands are to be corrected as to their indications, then a, plurality of cams and a suitable selecting means should be provided as shown. By use of the described apparatus, an accurate indication may be secured at any time that the indication is incorrect, it being assumed, of course, that the cam contour will be manufactured as closely as possible to the predicted capacity of the particu-' lar design.

Wherever in the specification and claims reference is made to a cam having a bendable active portion, it should be understood that I intend to comprehend by such term any cam capable of being deformed or changed as to local points on its active surface.

I claim:

1. In radio receiving apparatus the combination of tuning and indicating means, connections including a rotatable cam between the tuning and indicating means said cam having an invariable connection to the tuning means for rotation therewith, the cam having its active surface capable of local variation whereby to correct the indication of individual frequencies.

2. In radio receiving apparatus the combination of tuning and indicating means, connections including a rotatable cam between the tuning and indicating means said cam having an invariable connection to the tuning means for rotation therewith, the cam having a deformable flange constituting its active surface, whereby to enable correction of individual frequencies.

3. In radio receiving apparatus, the combination of tuning means, indicating means and band selecting means, a connection between the tuning means and indicating means, a plurality of cams in said connection, said cams having active surfaces capable of variation and means operated by said band selecting means for selecting the cam and connecting to the indicating means the cam intended for use with the individual band.

4. In combination, tuning means capable of variation to receive frequencies in different bands and indicating means, connections therebetween for effecting movement in unison, said connections including a plurality of cams adapted to be selectively operatively connected, manually operated means for selecting the cam corresponding to a particular band and means on said cams permitting adjustment of local points on the active surfaces whereby to enable correction of the indications transmitted thereby.

5. In combination, tuning means and indicating means and connections therebetween, said connections including a plurality of cams, racks reciprocated by said cams, a shaft for operating the indicating means, pinions on the shaft engaging said racks, a band switch and means operated by the band switch for selectively engag ing said pinions with said shaft. 7

JOHN L. McWEENY. 

